v2/v2.5 feeding, compression, motor, etc questions

Discussion in 'Gun Building, Modifications & Repairs' started by aotsukisho, Jul 6, 2019.

  1. aotsukisho

    aotsukisho Well-Known Member

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    Hi everyone, I have quite a few specific questions pertaining either to the v2 or v2.5 extended gearbox builds I’m doing.

    Trying to troubleshoot feeding (80% or so of shots ‘wump’) and low fps issues (~150fps with an M170) in my v2.5 AR-10 led me to all sorts of diagnostic techniques, including the nozzle-bucking lip seal testing with paper over the magazine feed opening and verifying compression by pushing on the piston while holding the nozzle. There are a few other things that I believe are factors that nobody seems to have talked about.

    1. Different brand tappet plates often have different fin profiles, which in turn adjusts the nozzle depth timing in the same way that sector gear chips do. On a related note, DSG installations instructions have you chop the bottom of the tappet fin off – does this have any useful applications in a normal rate of fire build or does this just lead to an increased risk of misfeeds but it a necessary evil for the mechanical needs of DSG applications?

    2. People often get into arguments about which sector gear chips are most effective, the lobed profile versus circular/bearing type, versus HunterSeeker5’s 3d printed design that resembles a marine tail fin. Related to my first question, I am assuming there is an ‘optimal’ profile for a range of RoF similar to how we have optimal cylinder venting for ranges of barrel lengths. Are sector delay chips always supposed to be installed?

    3. I’ve read a lot about sanding the front of tappet plates in order to extend the nozzle further forward, somehow this leads to better feeding? I was under the impression that the sector gear and tappet profile dictates how far the nozzle is pulled back, which allows bbs to enter the hopup chamber and be seated in the packing squished by the nub. In order for a wider feeding opening to occur, a nozzle of shorter length equal to the amount of tappet plate face removed should be used, correct? All tappet face sanding does is control how far forward the nozzle rests, which does not widen the feeding window whatsoever.

    4. Is there a database with information on which packing lips seal well with different packings in different hopup chambers? I’ve read about Prometheus Purple not fitting properly in Prowin hopups, and that sometimes packing lip sanding is necessary for proper feeding. This is something I would like to see data on, but I understand this is both difficult and expensive to test properly

    5. Are certain hopup chambers/packings incompatible with certain barrels? I have used Modify Baton Ryusoku Hards with Madbull/ZCI barrels and they do not work in Retro Arms hopups but do in Krytac hopups. I have also used the basic G&G Green with Krytac stock brass barrels and they do not work in a G&G hopup but G&G/ZCI barrels do. Normal operation when they work, misfeeds and bbs getting stuck if they don’t. Hop settings were dialed to just enough to hold the bbs in the barrel when held vertically, and bbs did fall through with no hop applied so it wasn’t a nub tension issue.

    6. I noticed some nozzles are very wobby (able to move tip around regardless of extension/retraction) on some cylinder heads when used on some tappet plates. Is this an issue in practice? My Retro Arms cylinder head/nozzle/tappet plate build has almost no wobble but a stock Classic Army gearbox when used with an SHS nozzle has it be very wobbly despite it fitting properly onto the tappet plate, and having what I’d say is a normal amount of tolerance around the cylinder head tube. Both of them fed fine, but I did not test compression or chrono at all in the wobbly one.

    7. Does the profile of nozzles matter? Some nozzles have that step or necking on them, while others are straight barrel up to the tip beveling. I’ve had stepped nozzles get stuck on hopups before leading to multi feeding and jamming before, is there a benefit to using them over the consistent diameter ones?


    Now there are some power delivery issues I’ve had working on a few guns

    1. I bought a ZCI High Torque motor, and noticed that reviews say it is longer than most normal long-type motors, and observed that it is true after I received it. Bottoming out in the motor plate still results in suboptimal meshing in multiple grips – KWA TK.45, G&G ARP9, ZCI A2 style. The only motor grip it fits and properly meshes in is an old G&G Raider-L 416-looking grip. Can this be rectified, and what is the best way…sanding the motor endbell down? Sanding the motor plate cradle? Washer between motor plate and grip? Washer between grip and gearbox? Are there any motor plates known for having deeper motor endbell cradles?

    2. I have another 22-turn neodymium motor periodically having trouble cycling an M140 spring in an 18:1 ratio gearset hooked up through a mosfet. It will fire once or a few times normally, then get ‘stuck’ and sound like it’s having trouble pulling the spring back for a few times until for no reason it will start working again. This pattern continues regardless of the state of charge of my battery, a 2s 1200mAh 25/50C lipo. This problem goes away entirely when using a 3s 1000mAh 20/40C lipo. There is no lipo cutoff enabled, could this be related to an active braking setting? There is nothing else I can think of that has an effect on seemingly randomized geartrain misbehavior. JG blue neodymium motor, Retro Arms gearbox shell, Classic Army gears, bearing on the bevel and bushings on the spur and sector shimmed properly enough to sound ok when it decides to work.


    Also have a question for those of you with Krytac Trident guns, I bought a Krytac Trident QSC spring guide off Evike as a replacement and it came with a philips head machine screw in the back where the stock gets bolted in. I removed this screw and it looks like an M3x??mm one, and found out that it holds the front of the spring guide and thus the bearing together. It cannot be installed without the screw, and even if it could it is too small to accept buffer tube screws. Does the Trident not have an AEG style buffer tube attachment? I do not have a completed gun in front of me to compare to.

    Thanks for the read everyone
     
  2. Guges Mk3

    Guges Mk3 Administrator Staff Member Administrator Supporting Member Lifetime Supporter

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    So many questions...break it up into multiple threads so we can stay on one subject.
     

  3. Lefse

    Lefse Well-Known Member Supporting Member

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    Those are a lot of questions indeed, but I'll try and answer the majority of them.

    1. Cutting the tappet fin is only necessary for DSG builds, it's to avoid tappet timing issues. It may be beneficial in extreme ROF SSG setups, but those setups are difficult to feed anyway.

    2. I generally try to avoid sector chips, they've caused more issues than they've solved for me. They may assist low performance magazines in moderate to low ROF setups, so they're more of a "bandaid" than actual upgrade.

    3. Sanding the tappet plate is primarily done to improve air seal between the nozzle and hop-up rubber, it's not intended as a feeding related mod. What you describe might work in certain setups, but if the nozzle is the correct length it should be retracted slightly further back than the BB chamber anyway.

    4. Unfortunately I doubt such a database exists, we simply have to deal with the varying tolerances of the airsoft industry.

    5. There can be varying tolerances and standards on barrel and hop-up chambers, so certain barrel can be a very tight fit in certain hop-up chambers.

    6. Again, this is related to the relatively sloppy tolerances of the airsoft industry.

    7. I imagine the different nozzle profiles have to do with the different inner profiles of the hop-up chambers. I usually just use nozzles that are designated to work with the gun, it usually works well.

    Phew, time for the second round.

    1. Again, sloppy tolerances and multiple different standards at play. If you have a rotary tool or bench grinder you can try and shorten the shaft a tad at the pinion end. Be careful not to grind off too much material on the "D section".

    2. I'm guessing this motor has what is called "dead spots" on the commutator.
     
  4. aotsukisho

    aotsukisho Well-Known Member

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    Guges - I know, but I would have a difficult time cutting up the first part as they are essentially feeding issues and me going down the list and thinking how each part has an affect on the mechanical process. The second question I agree with you, it could have been its own thread sorry

    Lefse - thank you for the insight and taking the time to help me out, it is appreciated
    1.1 - I see that it's because the second half's timing post interferes with the bottom of the fin, I was wondering mainly because if the bottom half of the tappet fin is unnecessary for DSG/high ROF builds, why is it not done for slower builds when the tappet/nozzle is moving more slowly and thus theoretically can feed more reliably. Nothing too important

    1.2 - You're saying that the longer 'open' window is more forgiving for magazine springs that feed slower either due to heavier bb's than designed for or just a weak follower spring in the first place. This makes sense. I noticed that the SHS normal v2/3 gears do not have modifications around the timing post, but their "SR25" v2.5 sector has a bearing around it. Assuming people upgrading gears must be wanting to shoot hotter and heavier, this now is an obvious design choice. I do notice that Siegetek (and others) have a lobe rather than a post, I assume that is just another way to have an extended feeding period.

    1.3 - From what I understand though the sanding of the tappet plate only increases maximum depth the nozzle reaches into the packing when released, the retraction distance is the same as that is completely controlled by the sector gear timing post pull-back and its interaction with the tappet plate fin profile. If that were so then using a slightly longer nozzle - say if you were to sand off 0.5mm of the tappet plate, instead would provide the same benefit without having to go through the work of modifying the tappet plate assuming it still feeds properly correct? If the opposite is done, sanding the tappet by 0.5mm but decreasing the nozzle length by 0.5mm and achieving the same air seal, the minimum depth of nozzle protrusion will be 0.5mm shorter which would mean the feeding window is 0.5mm longer while keeping the fully-released nozzle depth identical.

    1.4 - figures

    1.5 - Proper installation of a barrel+packing into the chamber is always to bottom it out right? Sometimes there's slight forward-back play that I can nudge the barrel without interfering with the clip on the hopup unit and it this will most definitely affect compression.

    1.6 - figures

    1.7 - Yes, I noticed differences between the SHS aluminum M4 nozzle, Retro Arms aluminum M4 nozzle, and ZCI aluminum M4 nozzle - SHS has a standard looking profile step, Retro Arms has no step, and ZCI has a step much closer to the tappet side. If this is to direct a bb into the proper location while retracting, I would think a linear conical gradient would work best?


    2.1 - I have gotten the pinion as low as possible on the motor shaft without it touching the collar thing that supports the shaft and it still binds when the motor depth screw and bevel gear are bottomed out furthest away from each other. The shaft does not touch the ARL ratchet face as the pinion binds on the bevel gear first so shaft length clearance is not a problem, and pinion is an SHS so it meshes with all the bevel gears in the gearboxes I've tried it on (SHS, Classic Army, KWA). I was also unable to bend tabs on the motor cans with my tools so I am not able to swap endbells which I am familiar with due to working on 130 size motors in Mini-Z's and Nerf. I might just have to buy different style and brand grips and see what works.

    2.2 I will inspect the commutator, thanks. I've never had comm buildup without a change in operational sound happen before, just motors that blew only one coil leading to poor startup performance depending on resting angle.